Chain saw construction



, Aug. 22, 1944. z D J SMITH I 7 2356 437 CHAIN SAW, CONSTRUCTION FiledJun 9, 1941 for engagement with the saw,

' is made up of inner Patented Aug. 22,, 1944 2,356,437 g V CHAIN sawCONSTRUCTION,

Donald J. Smith,

. Canada, assignor Worcester,

setts Application June 9, 1941, se'rn1N0.39 7,'194 r 2 Claims. (c1.143-135) a V v I 5 to flex-around the sprocket The lattenas will= Thepresent invention relates to chain saws and-particularly toa drivesprocket construction by which to obtain a positive andsubstantiallyfriction free drive for the saw chain.

In prior devices of this character, the driving element has beenprovided with rollers or pins as shown for example in the Arsneau PatentNo. 2,060,547.

Vancouver, British C olumbia, to Reed-Prentice Corporation,-

Mass., in. corporation of Massachuand chain While in the patentedconstruction,-the driving element is adapted to have line contact withthe saw chain, the contact between the sprocket and the chain isrelatively small and the wear on the parts is excessive. One oftherprincipal objects of the present invention is to provide a sprocketand chain, so arranged that the sprocket has fiat driving surfaces ofsubstantial area in contact with corresponding flat, surfaces on thelinks of the chain, and with these surfaces 'so positioned that there isno frictional drag between the chain and sprocket as the chain isengaged by the sprocket.

In the Brown et al. Patent No. 596,802, the

be understood; is suitably attached to :a-d'rive shaft, not shown,.andthe :saw chain-risdriven. by the sprocket as the latter rotates in thedirec-' tion of the arrow. l I

Each of the outer links 2, as shown,.is centrally notched, as at 5, toreceive and to engage with the outer end of the teeth 4a of thesprocket, and these outer links, by engagement with the, sprocket teeth,tend to support the saw chain. in a predetermined radial position withrespect to the-sprocket, as it will be apparent that the chain" cannotmove radially inwardly on the. sprocket while the links are inengagement with the teeth.' The outer links, being spaced apart thushave a substantially broad surface contact with the ends of the sprocketteeth and twisting or sidewise rocking of the chain on the sprocket isprevented.

driving element is provided with notches to receive inwardly extendinglugs formed on the outer links of the chain, and between the notches Vthe element engages with the inner links to suprock on the sprocket, andwill always be held at a predetermined of the sprocket.

Other and further objects and advantages of radial distance from theaxis the invention will hereinafter-appear from the following detaileddescription taken in connec- 7 tion withjthe accompanying drawing, inwhich- Fig. 1 is a side elevation of the sprocket embodying theinvention, with a saw chain in position on a part thereof.

Fig. 2 is a sectional view alon the line 2-2 of Fig. 1, looking in thedirection of the arrows. Fig. 3 is a fragmentary view of the chain withthe outer links removed.

With reference to the drawing, the saw chain links I pivotally connectedby outer links 2, with pins 3 providing a pivotal connection between thelinks to permit the chain tion of which, when the chain with the notches5 in the The rearward face of each of the inner links I has a fiatangularly disposed surface 6, the posiis wrapped around the'sprocket, isprecisely parallel to and in en-, gagement with the leading fiat drivingsurface 1 of a sprocket tooth and in a position to engage ,with thetooth 4asubstantially over the entire length thereof, as shown inFig. 1. It will be obvious that the inner link surfaces 6 areproportioned accurately with respect to the notches r 5 so that as thechain flexes around the sprocket the sprocket teeth surfaces 1 willstill engage the surfaces 6' while the points thereof engage 'outerlinks. 1

The forward lower corner of eachinner link I is cut away, as at 8, sothat there is no'engagement between the rearward surface of eachsprocket tooth and thefollowing inner link, so that any frictional dragonthe sprocket or chain from the non-driving surfaces of the sprocketteeth and chain links is howeventhat the inner edge of each inner link Imay have a relatively secting' with the surface 6 and in position toengage'with the corresponding surface' I 0 on the 7 sprocket.

It will be understood that the angularity of the surfaces 6 and l on aninner link and on the sprocket respectively is such that the angularthrust exerted on the link by the sprocket tooth does not tend to urgethe teeth outwardly with respect to the sprocket, but transmitspractically all of the driving power tangentially of the sprocket, aswill be apparent. 'The drivingsurface 1 onthe leading face of eachsprocket tooth preferably extends at an angle of approximately avoided.It will be noted,

small flat surface 9 internortion receivable between adjacent teeth ofthe sprocket, and providing a fiat end surface .closei 'ivengageablewith the leading flat driving sur- {ace ofasprockettooth when thechainis curved withthe'iorwardedge of the next succeeding 10 v pairs, witheach of said inner links having a =15' around; the; sprocket for drivingthe'same, and I link, of the-chain being cut away to avoid engagementwith the trailing face of a sprocket tooth, each pair of ;links in saido uter serie's pro viding alined" notchesv in theirlower edges toengagewiththeiend. of a. tooth of said sprocket,

Ionsupportingg the chain radiallyof the sprocket axis, and to preventrocking of the chain on a sprocket, as the chain is driven by theengaged flat surfaces ofa sprocket-tooth and inner link.

2. A chain saw construction, comprising in combination a'rotatabiydriven sprocket having radial teeth each providing a flat drivingsurface and a chainsaw cooperating with said sprocket comprising aseries of inner links pivotally connected on opposite sides by series ofouter links arranged inpairs, with the combined widths of an inner linkand two outer links sub stantially equal to the width of a sprockettooth, each pair of outer links providing alined notches in their loweredges to engage with the end of a teeth of said sprocket to support thechain ra- 'dially of the sprocket axis and thereby prevent rocking ofthe chain 'on the sprocket, and with each inner link providing a fiatdriving surface in complete 'face-to-face engagement with the leadingiiat driving surface of a: sprocket tooth when the chain iscurved-around thesprocketi DONALD J. sMrrH."

